On 01/29/2019 10:21 AM, Ard Biesheuvel wrote:
Move the x86 EFI earlyprintk implementation to a shared location under
drivers/firmware and tweak it slightly so we can expose it as an earlycon
implementation (which is generic) rather than earlyprintk (which is only
implemented for a few architectures)
This also involves switching to write-combine mappings by default (which
is required on ARM since device mappings lack memory semantics, and so
memcpy/memset may not be used on them), and adding support for shared
memory framebuffers on cache coherent non-x86 systems (which do not
tolerate mismatched attributes)
Note that 32-bit ARM does not populate its struct screen_info early
enough for earlycon=efifb to work, so it is disabled there.
Signed-off-by: Ard Biesheuvel <ard.biesheu...@linaro.org>
---
Documentation/admin-guide/kernel-parameters.txt | 8 +-
arch/x86/Kconfig.debug | 10 -
arch/x86/include/asm/efi.h | 1 -
arch/x86/kernel/early_printk.c | 4 -
arch/x86/platform/efi/Makefile | 1 -
arch/x86/platform/efi/early_printk.c | 240 --------------------
drivers/firmware/efi/Kconfig | 6 +
drivers/firmware/efi/Makefile | 1 +
drivers/firmware/efi/earlycon.c | 208 +++++++++++++++++
9 files changed, 222 insertions(+), 257 deletions(-)
[...]
+static int __init efi_earlycon_setup(struct earlycon_device *device,
+ const char *opt)
+{
+ struct screen_info *si;
+ u16 xres, yres;
+ u32 i;
+
+ if (screen_info.orig_video_isVGA != VIDEO_TYPE_EFI)
+ return -ENODEV;
+
+ fb_base = screen_info.lfb_base;
+ if (screen_info.capabilities & VIDEO_CAPABILITY_64BIT_BASE)
+ fb_base |= (u64)screen_info.ext_lfb_base << 32;
+
+ if (opt && !strcmp(opt, "ram"))
+ fb_prot = PAGE_KERNEL;
+ else
+ fb_prot = pgprot_writecombine(PAGE_KERNEL);
Can you determine the default from the UEFI memory map?
Also, doesn't the current logic map it as WC on x86 too? Is that
intentional?
Alex
+
+ si = &screen_info;
+ xres = si->lfb_width;
+ yres = si->lfb_height;
+
+ /*
+ * efi_earlycon_write_char() implicitly assumes a framebuffer with
+ * 32-bits per pixel.
+ */
+ if (si->lfb_depth != 32)
+ return -ENODEV;
+
+ font = get_default_font(xres, yres, -1, -1);
+ if (!font)
+ return -ENODEV;
+
+ efi_y = rounddown(yres, font->height) - font->height;
+ for (i = 0; i < (yres - efi_y) / font->height; i++)
+ efi_earlycon_scroll_up();
+
+ device->con->write = efi_earlycon_write;
+ return 0;
+}
+EARLYCON_DECLARE(efifb, efi_earlycon_setup);
